1. Field of the Invention
The present invention relates to an apparatus and method for determining the right of use of a bus, such as an IEEE 1394 serial bus.
2. Related Background Art
Various image processing apparatuses and systems are known that transmit command statuses via a serial bus to a plurality of modules or to a plurality of apparatuses.
In addition, for the transmission of binary monochromatic image data, which has a comparatively small, image processing apparatuses and systems are well known that transmit image data and command statuses via a serial bus.
However, when taking into account the transmission of color image data, which has a comparatively large volume, or the occurrence of a plurality of jobs for each of which the transmission of image data is required, the conventional transmission of data performed via a serial bus is not practical because the amount of data that can be transmitted in a unit hour is small, and accordingly, the transmission of data requires an extended period of time.
This problem can be resolved to a degree by increasing the transmission speed of the serial bus. However, when the conventional serial bus is employed for an image processing apparatus, such as a copier, for which real-time image data transmission is required, the intermittent command status transmissions that occur interfere with the transmission of image data, and a time by which the transmission of image data can be completed can not reliably be ascertained. Thus, as it is difficult for a serial data bus to be employed for an image processing apparatus for image data transmissions, a dedicated parallel bus must be used this purpose.
On the other hand, since there is an increased demand for a reduction in the sizes of such products as copiers, which are generally used in offices, and concurrently a request that their functions be improved, internally these common office products do not have enough space to accommodate a dedicated parallel bus to be used only for the communication of image data.
To resolve the above shortcomings, it is one objective of the present invention to provide an image processing apparatus and an image processing system that can perform the steady, high speed transmission of image data via a serial bus, even when command statuses and a comparatively large quantity of color image data must be transmitted, or even when conflicts develop among a plurality of jobs for which the transmission of image data is required.
To achieve the above objective, according to the present invention an image processing apparatus, which connects together a plurality of modules via a high-speed serial bus along which at least one isochronous packet and at least one asynchronous packet, which are assigned for a predetermined number of channels, can be sequentially transmitted during a single transmission cycle, and which transmits image data to the plurality of modules by assigning to the isochronous packet the transmission to the modules of image data and by assigning to the asynchronous packet the transmission of a command status, comprises:
determination means for, when a plurality of jobs, including the transmission of image data, are pending, determining whether the number of channels available in one cycle is adequate for the number of pending jobs;
preference determination means for, when the determination means ascertains that the number of channels available is not adequate, determining preferences to be assigned to jobs in accordance with the periods of time required to execute the jobs; and
change means for dynamically changing the execution timings for the jobs in accordance with the preferences determined by the preference determination means.
Furthermore, to achieve the above objective, according to the present invention, provided is an image processing apparatus, which connects together a plurality of modules, via a high-speed serial bus along which at least one isochronous packet and at least one asynchronous packet, which are assigned for each of a predetermined number of channels, can be sequentially transmitted in one transmission cycle, and which transmits image data to the plurality of modules by assigning an isochronous packet for the transmission of image data to the modules and by assigning an asynchronous packet for the transmission of a command status to the modules, wherein a module that performs the transmission of image data requests a right of use for the high-speed serial bus before beginning a transmission and transmits the image data only after obtaining the right of use for the high-speed serial bus, and wherein an arbiter is provided that, when the right of use for the high-speed serial bus is requested by two or more modules, assigns the right of use for the high-speed serial bus first to a specific module selected from among the requesting modules.